The applicant's long-term career plans are to conduct research and teaching on indoor environment, such as indoor air quality and thermal comfort in buildings. In particular, the applicant will emphasize the research on energy-efficient ventilation system for applications to occupational safety and health. Indoor environment is important to a worker's health and welfare, because more than half of the U.S. workforce is employed indoors, and up to 90 percent of a typical worker's time is spent indoors. Also, worker's productivity is related to the indoor environment, such as the indoor air quality and thermal comfort. Poor indoor environment design has cost billions dollars due to productivity loss of the working American. The aims of the proposed investigation are to develop an integrated design tool to analyze combined problems of indoor air quality (IAQ) and thermal comfort for an entire building. The integrated tool will consist of three major components: building models, a heating, ventilating, and air-conditioning (HVAC) model, and mass and heat source/sink models. The building models will use a simplified computational-fluid-dynamics model to calculate IAQ and thermal comfort in a single zone and a multi-zone model to link the heat and mass transfer between zones for an entire building. The HVAC model will use modules that can be easily used to form different HVAC systems. The mass and heat source/sink models will use the coupled program of the simplified computational-fluid-dynamics and an energy analysis program as well as various dispersion models. The integrated design tool will be validated by experimental data of LAQ and thermal comfort obtained in a building. The integrated design tool can be used to evaluate IAQ and thermal comfort in terms of contaminant concentrations, the mean age of air, ventilation effectiveness, airflow pattern, air velocity, air velocity fluctuation, air temperature, relative humidity, percentage dissatisfied people due to draft, and percentage predicted dissatisfied people in an entire building.